Re: [akpm-mm:mm-unstable 272/272] include/linux/stddef.h:8:14: error: called object is not a function or function pointer

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 2 May 2025 05:02:14 +0800 kernel test robot <lkp@intel.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> head:   ea17e4fdc13cae144d90ce8561c2f50a49492037
> commit: ea17e4fdc13cae144d90ce8561c2f50a49492037 [272/272] jfs: implement migrate_folio for jfs_metapage_aops
> config: arm-randconfig-002-20250502 (https://download.01.org/0day-ci/archive/20250502/202505020405.YzD9aNCo-lkp@intel.com/config)
> compiler: arm-linux-gnueabi-gcc (GCC) 7.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250502/202505020405.YzD9aNCo-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202505020405.YzD9aNCo-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from include/uapi/linux/posix_types.h:5:0,
>                     from include/uapi/linux/types.h:14,
>                     from include/linux/types.h:6,
>                     from include/linux/blkdev.h:8,
>                     from fs/jfs/jfs_metapage.c:7:
>    fs/jfs/jfs_metapage.c: In function '__metapage_migrate_folio':
> >> include/linux/stddef.h:8:14: error: called object is not a function or function pointer
>     #define NULL ((void *)0)
>                  ^
>    include/linux/pagemap.h:1234:31: note: in expansion of macro 'NULL'
>     #define filemap_migrate_folio NULL
>                                   ^~~~
>    fs/jfs/jfs_metapage.c:238:7: note: in expansion of macro 'filemap_migrate_folio'
>      rc = filemap_migrate_folio(mapping, dst, src, mode);
>           ^~~~~~~~~~~~~~~~~~~~~
>    fs/jfs/jfs_metapage.c: In function 'metapage_migrate_folio':
> >> include/linux/stddef.h:8:14: error: called object is not a function or function pointer
>     #define NULL ((void *)0)
>                  ^
>    include/linux/pagemap.h:1234:31: note: in expansion of macro 'NULL'
>     #define filemap_migrate_folio NULL
>                                   ^~~~
>    fs/jfs/jfs_metapage.c:641:10: note: in expansion of macro 'filemap_migrate_folio'
>       return filemap_migrate_folio(mapping, dst, src, mode);

#ifdef CONFIG_MIGRATION
int filemap_migrate_folio(struct address_space *mapping, struct folio *dst,
		struct folio *src, enum migrate_mode mode);
#else
#define filemap_migrate_folio NULL
#endif

well that's odd.  I guess it was only anticipated that
filemap_migrate_folio would be used in a struct initializer.

Should this new JFS migration code be wrapped in #ifdef CONFIG_MIGRATION?